Bringing together the Apache Cassandra experts from the community and DataStax.

Want to learn? Have a question? Want to share your expertise? You are in the right place!

Not sure where to begin? Getting Started

 

question

melki avatar image
melki asked Erick Ramirez answered

Replicas and copies of data when nodes are down

CREATE KEYSPACE machine_tools WITH REPLICATION = {
  'class': 'NetworkTopologyStrategy',
  'dc-1': 1,
  'dc-2': 3,
  'dc-3': 3
};

Let us suppose if dc-1, dc-2 and dc-3 have 5 nodes each. During write operation one node is down in each datacenter. As per the replication factor in each datacenter, is it safe to say that I will have 6 copies of a row across three datacenters.

replication
10 |1000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 1.0 MiB each and 10.0 MiB total.

1 Answer

Erick Ramirez avatar image
Erick Ramirez answered

Your question doesn't make sense to me. There are 7 replicas in total based on the keyspace definition you provided.

If one node is down in each DC:

During write operation one node is down in each datacenter.

then with 3 DCs you have 3 nodes down meaning that you are left with 4 live replicas. I'm not sure where you got 6 from. Cheers!

Share
10 |1000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 1.0 MiB each and 10.0 MiB total.